1. Field of the Invention
The present invention generally relates to a device for detecting objects on a windshield of a motor vehicle. More particularly, the present invention relates to a device for detecting objects on a motor vehicle windshield having an imaging unit with an optoelectronic sensor array and a lens that images a windshield section on a photosensitive surface of the sensor array and that is focused on this windshield section. Such a device also including an evaluation unit that receives electrical signals generated by the sensor array for evaluating the windshield section imaged on the photosensitive surface of the sensor array.
2. Background Art
Such a detection device, which is also designated as a rain sensor, is known from EP 0 832 798 A2. This known detection device includes an imaging unit for imaging water drops on the windshield of a motor vehicle on a camera sensor, whose lens is pointed towards the windshield from the interior of the motor vehicle and is focused on the detected windshield section. The camera sensor is arranged looking forwards in the travel direction in the region of the interior rearview mirror. The detected image data is evaluated by an evaluation unit that also controls a wiper motor as a function of the detected image data.
This detection device further comprises a transparent film that is used as a focusing screen and that is pasted onto the surface of the windshield in the region of the windshield section detected by the imaging unit. The transparent film is used for an improved image of raindrops by canceling out a background image on the photosensitive surface of the camera sensor. Due to the required use of such a transparent film, the imaging unit of this detection device can only be pointed towards such windshield sections associated with the secondary field of vision of the driver or the passenger. As is the case here, looking at the secondary field of vision can be used, in general, to represent the viewing conditions in the primary field of vision of the driver and passenger, e.g., for a windshield covered by rain. However, water drops can appear on the windshield of a motor vehicle only in certain parts of the windshield, e.g., in the primary field of vision of the driver. Such selective windshield coverings can occur, e.g., when single water drops fall from a tunnel ceiling while driving through a tunnel. In general, non-uniform interference of the field of vision is also the rule for dirty windshields.
In the features of separate windshield wiper motor control for the driver and passenger sides, detecting a windshield section in a common secondary field of vision for both fields of vision is also not sufficient.